1. Field of the Invention
The present invention relates to automobile airbag systems and apparatuses. More specifically, the present invention relates to airbags having independently inflatable overlapping cushions.
2. Description of Related Art
Safety belts are designed to protect the occupants of a vehicle during events such as automobile collisions. In low-speed collisions, the occupants are generally protected from impact with objects located inside the vehicle such as the windshield, the instrument panel, a door, the side windows, or the steering wheel by the action of the safety belt. In more severe collisions, however, even belted occupants may experience an impact with the car's interior. Airbag systems were developed to supplement conventional safety belts by deploying into the space between an occupant and an interior object or surface in the vehicle during a collision event. The airbag acts to decelerate the occupant, thus reducing the chances of injury to the occupant caused by contact with the vehicle's interior.
Many typical airbag systems consist of several individual components joined to form an operational module. Such components generally include an airbag cushion, an airbag inflator, a sensor, and an electronic control unit. Airbag cushions are typically made of a thin, durable fabric that is folded to fit into a compartment of a steering wheel, dashboard, interior compartment, roof, roof rail, seat, or other space in a vehicle. The airbag inflator is designed to produce a gas to rapidly inflate the cushion when needed. The sensors detect sudden decelerations of the vehicle that are characteristic of an impact. The readings taken by the sensors are processed in the electronic control unit using an algorithm to determine whether a collision has occurred.
Upon detection of an impact of sufficient severity, the control unit sends an electrical signal to the inflator. The inflator uses one of many technologies, including pyrotechnic compounds and pressurized gas, to produce a volume of inflation gas. The inflation gas is channeled into the airbag, rapidly inflating it. Inflation of the airbag causes it to deploy, placing it in position to receive the impact of a vehicle occupant. After contact of the occupant with the airbag and the corresponding deceleration of the occupant, the airbag deflates, freeing the occupant to exit the vehicle.
Airbag apparatuses have been primarily designed for deployment in front of an occupant between the upper torso and head of an occupant and the windshield or instrument panel. However, alternative types of airbags such as knee bolsters and overhead airbags operate to protect various parts of the body from collision. Side impact airbags such as inflatable curtains and seat mounted airbags also have been developed in response to the need for protection from impacts in a lateral direction, or against the side of the vehicle.
It has been discovered that various parts of the body require different levels of impact protection. For example, a seat mounted airbag may inflate beside an occupant in a vehicle seat to protect the pelvis and thorax of the occupant against lateral impact. The weight of the occupant may generally tend to slide with the pelvis; hence, it may be beneficial for the pelvic portion of the seat mounted airbag to inflate stiffly to provide comparatively firm protection. By contrast, the thorax is more sensitive and generally carries less mass, and thus should preferably be more softly cushioned during impact to avoid potential injury to an occupant's ribs.
Recently, dual chambered side impact airbags have been developed to provide a pressure differential between the pelvic and thorax portions of a side airbag. These airbags have two separate chambers, one on top of the other. The top chamber is used for providing impact protection for the thorax of an occupant in a seat and the bottom chamber is used to provide impact protection for an occupant's pelvis. In these systems an inflator is placed in a housing that has multiple orifices for channeling inflation gases into both chambers. The pelvic chamber is inflated to a higher pressure than that of the thorax chamber.
As with other types of airbags, thorax/pelvic airbags must be deployed rapidly in order to be effective. When a vehicle or some other object impacts the side of another vehicle, the side airbag must deploy in a matter of milliseconds. However, the airbag industry has experienced difficulty in deploying the lower pelvic portion of the side airbag in its intended position in a sufficient time period. This is because intrusion into the vehicle compartment generally occurs at or near the pelvic region due to the location of the colliding vehicle's bumper. If the pelvic portion of the side airbag is not positioned before significant intrusion occurs, the deploying side airbag may rebound off the armrest on the vehicle door, or otherwise be prevented from deploying in its proper position, possibly compromising the physical safety of the occupant.
Accordingly, it would be desirable to develop a side airbag system that can rapidly and timely position the pelvic portion of the inflatable cushion in its intended position to provide effective impact protection for a passenger. It would further be desirable to have an airbag assembly capable of having at least two inflatable portions that are inflated to different pressures while simultaneously maintaining its ability to position itself in a rapid and timely manner. It is also desirable to provide a side impact airbag cushion that is firm enough to prevent strikethrough of the occupant's pelvis while simultaneously being soft enough to provide adequate impact protection while limiting the possibility of being injured by the bag itself. Such a device is described and claimed herein.